Several systems have been proposed to implement intermodal transfer as a commercially viable alternative to the wholly road freight services which are available. Such systems include road semi-trailers or complete lorries on rail wagons, that is, "Piggyback" transport (T.O.F.C.), in Europe, North America and Australia, and the inland movement of containers or "swap bodies" (C.O.F.C.). The disadvantage of these systems is that although transfer is simplified, the equipment required to accomplish it is large, costly and, consequently, few and far between. The rail vehicles add considerable tare weight to the trunk haul and items of the equipment are carried about as additional tare rather than performing assets. That these systems are unsatisfactory is amply demonstrated by the number of attempts there have been to develop smaller or cheaper container transfer equipment, lighter "Piggyback" rail wagons and by the success of such systems as British Rail's Speedlink general merchandise trains which can involve considerable transhipment of goods between rail and road vehicles at each end of the rail journey.
The "Road-Railer" freight vehicles of the Bi-Modal Corporation of America represent one attempt to develop a vehicle which would enable the railway to provide a service comparable to those offering wholly road freight, door-to-door services using a conventional articulated lorry. However, "Road-Railer" vehicles are not compatible with other rail traffic and their use must be limited to dedicated services over specially authorized routes capable of taking their high (27 ton) axle loads. In essence, the vehicle is a road type, articulated lorry trailer, adapted by means of a special coupling and a retractable rail axle to run on rails. A train has to be formed behind a special truck to carry the front end of the first trailer and to couple to the rail locomotive. Once formed, such a train cannot be broken or reshunted in any normal railway manner without completely dismantling it because it becomes articulated throughout its length.
French Patent Specification No. 785,578 discloses an intermodal transport system having a bogie for supporting a wheeled rail wagon. The bogie is provided with road wheels and is connectible to the rail wagon by means of a fifth wheel coupling. A tractor pushes the bogie under one end of the railway wagon, thereby raising that end to be supported on the bogie. The tractor then drives round to reverse under the other end of the wagon, to which it is connected by a further fifth-wheel coupling so that the wagon can be conveyed by road by the tractor and the bogie. This system is limited in its application since there is no provision for a train of wagons, mounted on such bogies, to be formed, either for road or rail transport. Furthermore, the fifth wheel coupling arrangement needs to be provided on the wagon in addition to the standard couplings required to hitch the wagons together in a conventional train.